In an image processing apparatus for removing a noise signal from an image signal, a noise removal method employing multiresolution decomposition is widely known. In multiresolution decomposition, an image signal is divided into a plurality of frequency subband signals using a filter bank method or a Laplacian pyramid method such that during noise removal, noise removal processing can be performed on each of the divided bands with an appropriate intensity.
JP9-212623A discloses noise reduction processing employing wavelet transform as a multiresolution decomposition method. Here, wavelet transform is implemented on original image data to obtain a plurality of frequency subband components, whereupon noise reduction processing is implemented by performing coring processing on each subband component. Following the coring processing, the subband components are resynthesized through inverse wavelet transform, whereby noise reduction-processed image data are obtained.